US 7112255 B2
Self-supporting pleated fluid filter medium and method of making the same wherein the filter medium and accompanying flow-through border frame are of coated thermobondable materials, which are heat bonded together.
1. A method of assembling a selectively sized and configured pleated unit filter medium and a border frame which incorporates thermobondable materials comprising:
heat softening selected opposed edges of at least one thermobondable pleated unit filter medium layer;
compressing said opposed selected edges of said pleated unit filter medium into substantially flat border edges;
mounting said unit filter medium onto a compatibly sized and configured thermobondable flow-through border frame having selected filter medium support edges to receive and support said compressed border edges of said unit filter medium in facing relationship therewith; and
thermobonding said facing edges of said unit filter medium with said border frame.
2. The method of assembling the unit filter and border frame of
3. The method of
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12. The method of assembling the unit filter and border frames of
13. A method of assembling a selectively sized and rectangularly configured pleated unit filter and a compatibly configured border frame which filter medium incorporates at least one layer of up to 100% by weight melt blown fibers of approximately 0.3 to 35 micrometers and which includes a thermoplastic flow-through facing and a synthetic stiffener; the method comprising:
heat softening the pairs of opposed edges of said rectangular filter medium with suitable heating in the temperature range of 150° F. to 525° F.;
compressing said opposed heated edges to a substantially flattened form to have a depth/width calculably coordinated with the depth/width of the pleats of the pleated unit filter;
cutting said layered unit filter medium into a rectangular shape;
mounting said rectangular unit filter medium onto a compatibly rectangularly sized selectively layered thermobondable chipboard flow-through border frame unit having inwardly extending edges to receive and support said flattened border edges of said layered unit filter medium in facing relationship therewith;
ultrasonically welding said facing edges at a frequency of approximately 20 kilohertz (khz), said ultrasonic welding being accomplished on a moving assembly line with thermobonding varied spacing gaps in the range of approximately 0.05 to 0.3 inches, said compressing of said layered filter medium edges and said thermobonding of said facing edges being accomplished in at least two steps by respective pairs of spaced opposed edge compressing and ultrasonic thermobonding tools one pair of said ultrasonic tools being in line with the axis of movement of said facing edges and the other pair of aid ultrasonic tools being normal to said axis of movement.
14. The method of
This application is a division of application Ser. No. 10/119,997 filed Apr. 10, 2002, now U.S. Pat. No. 6,758,878 and which is incorporated herein by reference.
The present invention relates to a flow-through filter medium product and more particularly to a unique and novel unified filter medium, border frame therefore and method of assembling the novel filter medium to the border frame to assure a sturdy and stable unit filter arrangement for efficient treatment of a high velocity fluid stream.
It has been long known to utilize thermoplastic, melt blown materials for filtration purposes, attention being directed to U.S. Pat. No. 5,531,235, issued to C. B. Hassenboehler, Jr. et al on Jul. 2, 1996, which utilizes such an arrangement in the manufacturing of cigarette filters. Attention is further directed to the heat bonding arrangements disclosed in U.S. Pat. No. 5,652,041, issued to G. K. Buerger et al on Jul. 29, 1997; U.S. Pat. No. 5,709,735, issued to D. G. Midkiff et al on Jan. 20, 1998; U.S. Pat. No. 6,159,318, issued to Kyung-Ju Choi on Dec. 12, 2000; and, to U.S. Pat. No. 6,254,653, issued to Kyung-Ju Choi et al on Jul. 3, 2001. In addition to the heat bondable filter medium set forth in each of these aforementioned patents, attention also is directed to the border frame support units and manufacturing processes disclosed in certain of these aforementioned patents.
Recognizing the broad features of the prior art as taught by the prior art, the present invention provides an efficient, economical, and, straight forward structure for a unique filter medium with compressed edges which enhances both binding assembly and subsequent filtration efficiency. The present invention further provides a unique and compatible unified border frame member to cooperatively receive and support such novel filter medium of the present invention and which also enhances filter unit assembly sealing operations. In addition, the present invention provides a unique and novel unified assembly arrangement requiring a minimum of efficient and economical steps to sealingly join the novel filter medium and novel border frame member to produce an efficient, sturdy and stable filter unit, capable of ready installation for the filter treatment of high velocity fluid streams.
Various other features of the structural arrangement of the novel edge treated filter medium, novel support border frame therefore and the novel method, all as disclosed in a unified manner herein, will become obvious to one skilled in the art upon reading the disclosure set forth herein.
More particularly the present invention provides a unique fibrous filter medium which lends itself to ready assembly with the novel border frame arrangement also further described herein and to the unified novel assembly method also described hereinafter.
Specifically, the present invention provides a novel self-supporting pleated fluid filter medium including opposed upstream and downstream faces comprising at least one sheet of thermoplastic synthetic fibrous material which can be of low melt attenuated fibers with selected denier characteristics or a dri-laid blend of chopped fibers of selected size and diameter. The fibrous material should have at least a sufficient stiffness to provide for self-supporting pleats sufficient to maintain pleat form during an anticipated fluid filtering treatment velocity. Advantageously, the inventive sheet of thermoplastic fibrous material can be up to 100% by weight of preselected thermoplastic fibers comprising dri-laid blended chopped fibers comprising 0.5 to 40 denier fibers, with fiber lengths of 0.3 to 3 inches, or, if of melt blown material with fiber sizes in the range of approximately 0.3 to 35 micrometers.
In addition, the present invention provides a novel border frame member comprised of at least one strip of material, the strip being conformably sized to engage opposed peripheral edge faces of thermoplastic fluid filter medium to be bonded thereto.
Further, the present invention also provides a novel method of assembling the selectively sized and configured pleated unit filter medium and the border frame which incorporates thermobondable coated materials comprising: heat softening selected edges of at least one thermobondable unit filter medium layer; compressing selected edges of the unit filter medium into substantially rigid border edges; mounting the unit filter medium unto a compatibly sized and configured thermobondable border frame having selected filter medium support edges to receive and support the border edges of the unit filter medium in facing relationship therewith; and thermobonding the facing edges of the unit filter medium and the border frame in sealed relation.
It is to be understood that various changes can be made by one skilled in the art in one or more of the several features and parts of the novel filter medium and the novel flow-through border frame, as well as in one or more of the several steps of the inventive method described herein without departing from the scope or spirit of the present invention.
Referring to the drawings, which disclose advantageous embodiments of the unified inventive unit filter medium, the novel supporting flow-through border frame therefore; and, a schematic diagram of the novel method of sealingly assembling the unique unit filter medium and compatible supporting border frame:
In accordance with one feature of the present invention, the novel filter medium 2 (
It is to be understood that the aforementioned dimensional ranges can be varied accordingly with the understanding of the nature of the fluid stream to be treated. Advantageously, with thermoplastic fibers being used as a material, the fibers can be of up to 100% by weight of preselected fibers such as polyolefin, polyester, or nylon. If the fibers are of dri-laid blended chopped fibers, they are comprised approximately in the range of 0.5 to 40 denier fibers, and preferably of approximately 3 denier fibers. If melt-blown web is used, the fibers can be of diameters in the range of approximately 0.3 to 35 micrometers.
The selected fibrous material, advantageously can have a Gurley stiffness in the range of approximately 400 to 2000 milligrams (mg) and advantageously a Gurley stiffness of approximately 600 milligrams. Further, the selected fibrous material can have a Frazier permeability in the range of approximately 3 to 4000 cubic feet per minute, per square foot (cfm/ft2) and advantageously approximately 550 cubic feet per minute, per square foot (cfm/ft2).
In accordance with another feature of the present invention, the aforedescribed selected fibrous filter medium, which can be of one or several layers in thickness, can include a facing of thermoplastic netting of polyolefins or non-woven scrim material 6 (
In the embodiment disclosed the novel, rectangular border frame 11 can be formed from two similar flat strips 12 of material (only one of which shown in
It is to be noted in
In the first stage of the present invention, as thermobondable filter medium 2 which can incorporate at least one layer of up to 100% by weight thermoplastic fibers of dri-laid blended chopped fiber of approximately 0.5 to 40 deniers, or melt-blown fibers with diameters in the range of 0.3 to 35 micrometers, if of blended chopped fibers of approximately 0.3 to 3 inch lengths and which can include a thermoplastic flow-through facing and a synthetic binding stiffener, if the material so requires, is continuously fed past a pair of oppositely spaced blowers 23 which are arranged to blow a heated fluid such an air along the opposed edges 7 of filter medium 2 to soften such opposed edges. The temperature of the heated fluid, such as air, steam or conductive or radiant heating means can advantageously be in the temperature range of 150° F. to 525° F. It is to be understood that such temperature range of the heated fluid can vary depending on the nature of he fluid and the nature of the thermobondable filter medium being edge treated.
The filter medium 2 with opposed, heat softened edges 7 then passes between a first pair of spaced opposed compressing press or platen bars 8, as shown in
The edge compressed filter medium 2 is then cut or severed in any one of several manners, such as by spaced opposed appropriate cutters 24, and mounted as a unit filter medium 2 (
Once the unit filter medium 2 is appropriately and conformably mounted along edges 7 in assembled border frame 11, the assembled unit filter then is passed to spaced, opposed pairs of ultrasonic sealing sets 26 and 27 which sealing sets are positioned normally to each other and which also can be vertically “up-down” moveable to ultrasonically seal the sandwiched filter medium edges to the overlapping border panels. It is again to be noted in
As above-described, the flow-through border frame 11 can be of thermobondable chipboard. Further, the ultrasonic welding by welding sets 26 and 27 can be accomplished at a frequency of approximately 20 kilohertz (khz) with the welding being accomplished with gaps between assembled unit filters in the range of approximately 0.05 to 0.3 inches